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In multi-axis fused deposition modeling (FDM) printing systems, support-free curved layer fabrication is realized by continuous transition of the printer nozzle orientation. However, the ability to print 3D models with complex geometric (e.g., high overhang) and topological (e.g., high genus) features is often restricted by various manufacturability constraints inherent to a curved layer design process. The crux in a multi-axis printing process planning pipeline is to design feasible curved layers and their tool paths that will satisfy both the support-free condition and other manufacturability constraints (e.g., collision-free). In this paper, we propose a volumetric curved layer decomposition method that strives to not only minimize (if not prevent) collision-inducing local shape features of layers, but also enable adaptive layer thickness to comply with a new volumetric error-based surface quality criterion. Our method computes an optimal Radial Basis Functions (RBF) field to modify the fabrication sequence field, from which, the iso-surface layers are extracted to design the corresponding multi-axis printing tool paths. A method to fine-tune variable nozzle orientations on each resulting curved layer is then proposed to overcome possible collisions in high-genus geometries. To validate the concept and exhibit its potential, several support-free fabrication experiments and comparisons with the conventional geodesic field-based slicing are presented, and the results give a preliminary confirmation of the feasibility and advantages of the proposed method.

The newly emerged hybrid manufacturing platform that incorporates both additive manufacturing (AM) and five-axis machining modules makes it possible to manufacture parts of complex shapes with high finish-surface quality that are impossible to be produced solely by either machining or additive manufacturing. In general, a hybrid manufacturing process is signified by an alternating sequence of AM operations and machining operations that alternatingly build and machine an in-process workpiece into the final design shape. Aside from other considerations, collision avoidance between the in-process workpiece and both the cutting tool and the material-dispensing nozzle is one of the most critical constraints that affect the determination of the alternating sequence. Due to the newness of hybrid manufacturing technology, currently there has been few systematic studies of this collision avoidance problem in which the obstacles are in a constant state of growing, especially on nozzle collision avoidance which – though never an issue in the traditional 2.5-axis AM because the in-process workpiece is always below the printing nozzle – now becomes a real concern in hybrid manufacturing as the in-process workpiece now dynamically grows and is not constrained by the current build layer. The nozzle collision problem is particularly pronounced in metallic hybrid manufacturing where the nozzle compartment typically is large and has a complex shape. In this paper, we conduct a thorough study of this collision avoidance problem in hybrid manufacturing and present a deterministic algorithm for automatically generating a collision-free sequence of hybrid manufacturing with the least alternations for a solid part. Specifically, as long as the part can be represented in the so-called columnar form, and the build layers are either planar or on concentric conic surfaces, for any given tool and nozzle, our algorithm will automatically generate an alternating sequence of minimum length whose

Hybrid manufacturing incorporating additive manufacturing and subtractive machining can produce parts of complex geometries with high surface finishing quality which are impossible to be done by either additive manufacturing or subtractive machining alone. Additive manufacturing can fabricate complex parts which is difficult or even impossible to be made by subtractive processes; while machining operation after additive manufacturing can remove the staircase effect which inevitably appeared in additive processes. However, machining after one-off fabrication of entire part may not always applicable because machining tool may be blocked by the already-printed parts, especially for parts with slender features in close proximity. To solve the problem, alternating sequence between additive manufacturing and machining is introduced to the process planning of hybrid manufacturing. The remaining question is how many times of alternating sequence will be suitable for fabrication of the parts. There exists previous literature do optimization for minimizing the number of alternations by considering the accessibility of machining tool, however, the accessibility of nozzle has never been concerned. In practice, the workpiece in hybrid manufacturing grow in a non-uniform rate which the collision between nozzle and in-process workpiece is possible especially with a large metal additive nozzle. Therefore, the main objective is to fill up the gap in previous literature by introducing an inspection to ensure all the region can be accessed in the time of printing. To achieve this goal, the manufacturability metrics for additive manufacturing, which named printability, is first formulated for determining the accessibility of printing nozzle. Then, a rectification process is presented to rectify the alternating sequence generated by the algorithm from previous literature for satisfying the newly defined metrics. The optimality of this rectification process is proven for parts with slend